Trenching for Utilities

A trench for water, power or drainage looks like a simple ditch. It is also one of the most dangerous jobs on a farm, and the planning starts long before the engine does.

Key points

Call 811 and look for private lines before digging.
Choose a trencher or excavator to match soil and depth.
Follow local code for depth and materials.
Never enter an unsupported trench.
Record the route before you backfill.

What should you do before you dig a utility trench?

Call 811 a few days ahead so that public utilities can mark their buried lines. Private lines, such as a yard hydrant supply, a barn power feed or drain tile, are not marked by the utility, so research old plans and talk to previous owners or neighbors.

Then sketch the route, noting buildings, fence lines, trees, roads and drainage. Check what permits are needed. Electrical, plumbing and gas work usually has code and licensing requirements that vary by state and county.

Write down the dates and the 811 ticket information, and keep the markings intact until the job is done. If paint or flags are disturbed, stop and call again rather than guessing where a line ran.

Call 811 and wait for the markings
Look for private lines and drain tile
Check permits and inspection requirements
Decide who will install the line: you or a licensed contractor

Which equipment is best for trenching?

A walk-behind or ride-on trencher can cut long, narrow ditches quickly in suitable soil and is a good rental for a single project. A mini excavator is more flexible and handles rocks, roots and varied depths. A tractor with a backhoe attachment can also do the work.

Choose by soil, depth and length. A 5-acre homestead running a water line to a barn might be fine with a rented trencher. A long run through rocky ground may call for an excavator.

For hard or rocky ground, a trencher can chip teeth or jam. Ask the rental yard about the right chain for your soil, and ask them to show you the controls and safety features before you leave the yard.

How deep and wide should the trench be?

Depth and width depend on what goes in the trench, local code and frost conditions. Water lines may need to be buried below the frost line in cold regions. Electrical cable depth depends on the type of cable and conduit and on code.

Do not rely on a number from the internet. Ask your local building or electrical authority, water utility or a licensed installer what applies in your area.

How do you stay safe in and around a trench?

Trench collapse can bury a worker in seconds, and even a shallow trench can be deadly. OSHA has specific requirements for protecting workers in trenches, including sloping, shoring or trench boxes, safe access and a competent person on site. Learn what applies, and keep it in mind even on your own land.

Keep spoil piles and equipment back from the edge. Never stand or work in an unsupported trench. Watch for water entering the trench and for signs of cracking along the edge.

Water and weather change trench conditions fast. After rain, vibration from nearby equipment or freshly dug soil, walls that seemed stable may not be. When in doubt, stay out and call a competent person.

Do not enter an unprotected trench
Keep spoil and machines back from the edge
Provide a way out where people must enter
Watch for utilities and overhead lines

How do you lay and backfill properly?

Follow the pipe or cable manufacturer's instructions for bedding, warning tape and backfill. Many installations call for a clean bed of sand or fine material, with rocks kept away from the pipe. Tracer wire or marking tape helps others find the line later.

Backfill in layers and compact as directed so the ground does not settle into a dip over the trench. Leave a slight mound that will settle, and seed bare ground to prevent erosion.

If you are laying more than one line, such as water and electric, ask your installer or local authority about required separation. Do not share a trench unless code allows it.

What mistakes cause the biggest problems?

Skipping the locate call, burying a line too shallow, using the wrong pipe or conduit, and backfilling with sharp rocks are the common ones. Forgetting to record the route is another. Take photos and measure from fixed points before covering the trench, then note the route on a farm map.

A hand-drawn map with measurements from the corners of buildings is better than memory. File it with your farm records, and give a copy to the next owner when you sell.

When is it time to hire a licensed contractor?

Gas lines, high-voltage power, septic work and anything inspected by code usually call for a licensed professional. A contractor can also bring trench protection equipment. Check licensing, insurance and permits, and ask your insurance agent about coverage if a project involves hired labor.

When to get help: Hire a licensed electrician or plumber for electrical and plumbing work, contact your building authority about permits, and ask OSHA about trench safety if workers are involved. Talk to your insurance agent about coverage for hired labor.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

More in Loaders, Excavation & Property Maintenance

← Digging a Pond with Equipment Grading and Leveling with Equipment →